1. Field of the Invention
The present invention relates to speed measurement, and in particular, to a laser apparatus and method for speed measurement.
2. Description of the Prior Art
Speed measurement has long been used by traffic enforcement personnel in measuring the speed of vehicles. However, speed measurement is now becoming increasingly popular in a number of other applications. One such application is in the field of sports, where it has become popular to measure the speed of a ball, such as a baseball pitcher's pitches, a tennis serve, and a soccer shot, among others. Another application is in the measurement of the speed of a bullet fired from a gun.
Most of the currently-available speed measurement devices use the Doppler principle, where the target's interference with an emitted wave causes a reflection from the target. The wavelength of the reflected wave is used to determine the speed of the target. One drawback with such speed measurement devices is that they require a user to focus the device on the target, and they cannot be operated effectively without human intervention unless the target is guaranteed to cross the path of the device. This effectively limits the number of applications to which the device can be used.
Laser has also been used to measure the speed of moving objects. As one example, U.S. Pat. No. 5,812,249 to Johnson discloses a system having two opposing laser sources and detectors that are used to measure the speed of a passing vehicle. A significant drawback with this system is that the laser sources and detectors must be set up to be opposite to each other, so that this system is again limited in the number of applications that it can be used with.
Thus, there remains a need for an effective and accurate, yet inexpensive, apparatus and method for measuring the speed of an object, which is simple in construction, is convenient to use, and is capable of measuring the speed of a wide variety of objects in many different applications without the need for human manipulation or control.